Police are searching for a dirt-bike rider who allegedly hit and killed a minor who was riding an all-terrain vehicle in Plymouth on Sunday afternoon, said Reggie Zimmerman, spokesman for the Massachusetts Executive Office of Energy and Environmental Affairs. Zimmerman said the dirt biker hit the minor around 2 p.m. Sunday before fleeing the scene. Details on the minor’s age, gender, or residence was not being released Sunday night. Plymouth police, Massachusetts Environmental Police, and Massachusetts State Police are investigaing.